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October 17, 2006

Only 10% of the cells in your body are human. Wow! Really?

Yup, there are about ten times more bacteria as cells with human DNA in your body. According to Dr. Cynthia Sears at Johns Hopkins, your body contains something like 100 trillion bacteria from 500 to 1000 different species, compared to about 10 trillion of your own cells.

Happily most of them perform tasks that are useful or even essential to your survival. They live on your skin and eyes, in your mouth, nose, small intestine, and colon, but the majority live in your large intestine where they break down nutrients such as carbohydrates that you couldn’t otherwise digest.

Unfortunately, some bacteria that lie in your gut, such as E. coli, can also cause disease. For that matter, bacteria that live in your mouth as a sticky substance called plaque hardens into calculus or tartar and also secrete acids that dissolve your tooth enamel, causing tooth decay.

“Not only does the Earth contain more bacterial organisms than all others combined (scarcely surprising, given their minimal size and mass); not only do bacteria live in more places and work in a greater variety of metabolic ways; not only did bacteria alone constitute the first half of life’s history, with no slackening in diversity thereafter; but also, and most surprisingly, total bacterial biomass (even at such minimal weight per cell) may exceed all the rest of life combined, even forest trees, once we include the subterranean populations as well. Need any more be said in making a case for the modal bacter as life’s constant center of maximal influence and importance?”